1. Field of the Invention
The present invention relates to an image processing apparatus, computer readable medium storing program, image processing method, image capturing apparatus, printing apparatus and scanning apparatus which perform image processing on images. More particularly, the present invention relates to the image processing apparatus, computer readable medium storing program, image processing method, image capturing apparatus, printing apparatus and scanning apparatus which performs edge correction on the image.
2. Description of Related Art
Conventionally, when edge correction is performed on an image, the edge correction is performed on the image after gamma correction is performed on the image, or the edge correction is performed on the image before gamma correction is performed on the image. In such manners, there has been a problem that higher gain is applied on an area where signal level is low, and noise in the dark area of the image is greatly conspicuous. Moreover, since the gain is uniformly applied on the image, result of the edge correction is not satisfactory in a bright area of the image.
Conventionally for example, a Japanese patent application publication No. 55-92083 discloses an edge compensation circuit and a Japanese patent application publication No. 63-209373 discloses a video signal processing circuit as image processing apparatuses. In the disclosed edge compensation circuit, edge correction signal is generated based on image signal before gamma correction, and edge compensation is performed by superimposing the edge correction signal on the image signal after gamma correction. The disclosed video signal processing circuit includes an edge correction means for performing edge correction to an input video signal, a gamma correction means for performing gamma correction to the input video signal, and an adding means for adding an output video signal from the edge correction means and an output video signal from the gamma correction means.
However, in the disclosed edge compensation circuit, since the edge correction signal is generated based on the image after the gamma correction, there is a problem that the noise in dark area of the image is greatly conspicuous. Moreover, in the disclosed video signal processing circuit, there is a problem that level of the edge enhancement in bright area of the image becomes excessive.